I was classing pos and neg squarewave as ac, strictly speaking it is, however I nkow what your saying in the world of fabricators ac is what comes out of a mains transformer.
The positive half of the cycle gives you the electrode clean, and the neg side penetration of the base material, you can tell when clean has been used as there is a dark line each side of the weld (depending on gas used), some sets dont specify 'clean' on the panel, miller for one call it 'balance' same thing.
If its any use to you shawn I built a hf start to run from 12dc (for a 4x4), at the time I was looking at some that ran from 240v and used very little parts, let me know if your interested.